Claims:We claim:

1. A tractor seat assembly for attenuating road excitations and to reduce the vibrations induced by tractor engine in all six degrees of freedom, the seat assembly comprising:

• a seat;
• a seat mount;
• a seat base; and
• a plurality of suspension elements;

wherein the seat assembly is mounted on the tractor skid and the suspension elements are placed between the seat mount and seat base to make an integrated connection for providing six degrees of freedom to the seat assembly.

2. A seat assembly as claimed in claim 1, wherein the suspension elements are disposed at four corners of the seat mount connected to the seat base by means of a plurality of bolts.

3. A seat assembly as claimed in claim 2, wherein the suspension elements are configured as spring damping units for transferring or attenuating the forces or excitations in all six directions based on the stiffness and damping characteristics thereof in each of the possible six degrees of freedom.

4. A seat assembly as claimed in claim 2, wherein the suspension elements are configured as isolators circular in shape with a definite height and having no metal-to-metal contact to provide 100% isolation between the vibration source and the seat.

5. A seat assembly as claimed in claim 4, wherein each isolator comprises:

• an outer metal bracket rigidly mounted on the seat base;
• an inner metal bracket inserted inside this outer metal bracket,
• a guide for metal sleeve; and
• a bolt or pin inserted into the guide;
wherein the inner metal bracket acts as the support for a guide for connecting the seat to the seat base without any metal-to-metal contact therebetween.

6. A seat assembly as claimed in claim 5, wherein the guide is made of rubber.

7. A tractor seat assembly for attenuating road excitations and to reduce the vibrations induced by tractor engine in all six degrees of freedom, the seat assembly comprising: a seat; a seat mount; a seat base; and four isolators each disposed at one of the four corners of the seat mount connected to the seat base by means of a plurality of bolts.

8. A seat assembly as claimed in claim 7, wherein the isolators act as spring damping units for transferring or attenuating the forces or excitations in all six directions based on the stiffness and damping characteristics thereof in all six degrees of freedom.

9. A seat assembly as claimed in claim 7, wherein the isolators are configured circular in shape with a definite height and having no metal-to-metal contact to provide 100% isolation between the vibration source and the seat.

10. A seat assembly as claimed in claim 9, wherein each isolator comprises:

• an outer metal bracket rigidly mounted on the seat base;
• an inner metal bracket inserted inside this outer metal bracket,
• a rubber guide for metal sleeve; and
• a bolt or pin inserted into the rubber guide;

wherein the inner metal bracket acts as the support for the rubber guide to connect the seat to the seat base without any metal-to-metal contact there between.

Dated: this 02nd day of December, 2016. SANJAY KESHARWANI
APPLICANT’S PATENT AGENT , Description:FIELD OF INVENTION

The present invention relates to tractor seats. In particular, the present invention relates to tractor seats which can control vibrations produced both by road excitation and engine operation. More particularly, the present invention relates to tractor seat having six degrees of freedom (6DoF).

BACKGROUND OF THE INVENTION

In a mechanical system, the degree of freedom (DOF) is the number of independent parameters that define the configuration of the system. These parameters determine the state of any physical system, which are quite important for analyzing the components present in mechanical engineering, aeronautical engineering, robotics, and structural engineering systems.

The exact constraint mechanical design method manages the degrees of freedom to neither under constrain nor over constrain such a system.

Accordingly, the position of a single car (engine) moving along a track has one degree of freedom because the position of the car is defined by the distance along the track. A train of rigid cars connected by hinges to an engine still has only one degree of freedom because the positions of the cars behind the engine are constrained by the shape of the track.

Further, an automobile with highly stiff suspension is a rigid body traveling on a plane (a flat, two-dimensional space). This rigid body has three independent degrees of freedom, consisting of two components of translation and one angle of rotation. Skidding or drifting is a good example of an automobile's three independent degrees of freedom. So, the position and orientation of a rigid body in space is defined by three components of translation and three components of rotation, which means that it has six degrees of freedom. These six degrees of freedom (6DoF) refer to the freedom of movement of a rigid body in three-dimensional space.
Specifically, the body is free to change position as forward/backward (surge), up/down (heave), left/right (sway) translation in three perpendicular axes, combined with changes in orientation through rotation about three perpendicular axes, often termed pitch, yaw, and roll.

On this premise, the tractor seats are also subjected to mainly two kinds of vibrations. There are the vibrations induced by road excitations as well as the vibrations induced by tractor engine which is transmitted to the seat via skid.

Different strategies need to be adopted to control both these vibrations. For example, the former can be controlled by having dedicated suspension system with the spring damper assembly, which can be tuned to work in a 0–4 Hz range. The latter can be controlled by using isolation techniques.

PRIOR ART

US 2006261647 A1 discloses a seat having an oscillation frame (2) supported by spring mountings (3a,3b) and provided with an adjustable seat mechanism (6a,6b,8a,8b,10) acted on by at least two actuators (4a,4b). The signals from at least two acceleration sensors (11) adjacent respective linkage axes for the seat frame are fed to an electronic control for conversion into required setting forces (F1*, F2*) supplied as control signals to setting elements (S1, S2) for the actuators, for compensating the dynamic forces. However, this documents discusses only two degrees of freedom, i.e. for counteracting pitching or rolling movements of the seat, which is intended not only in for seats of the trucks and commercial vehicles but also passenger cars.

DE102008050192 (A1) discloses a vehicle vibration damping system with a vehicle seat upper part (1) and a vehicle base frame (2) movable vibrating with respect to each other by means of a pneumatic spring (9,33,45,53), characterized in that at least one support element (12,22,32,42,52) acting on at least one of the vehicle component (1), the inertia force of which with vibrating movement occurring from at least one of the vehicle component (1) acts on an adjusting unit (11,14,15; 21,23-25; 33-35; 41,44; 54,56) for continuous readjustment of at least one spring element relevant parameter of the spring element (9,33,45,53) for changing the vibration transfer function.

GB1266796 (A) discloses a resiliently mounted tractor seat comprises a bucket-seat 1 supported by a compression spring 8 in a housing 6, the upper link 3 of a four-bar linkage connecting the bucket to a base-plate 7 being of U-shape with the web pivoted to the housing and having a nose 28 projecting into the housing for engagement beneath a hook 29 to limit upward movement of the seat to the normal seating position shown in full lines in Fig. 1 and prevent excessive pivotal movement of the seat in travel over rough ground.

The hook is pivoted on the housing wall, urged by a spring 30 to locking position and released therefrom by a hand lever 31. The spring 8 is mounted between a lower abutment 9, adjustable by screw 11 and hand wheel 10 to suit the weight of the user, and an upper abutment 12 to which are welded bearing pins 13, 14 which project from the casing and have rollers 15, 16 received in recesses in bearing arms 17 projecting from the web 4. A helical torsion spring (24), wound on the common pivot 23 of the lower links 2, has one end bearing on the housing and the other end on the lower links 2 and, on release of the nose 28 from the hook 29, urges the seat to rise, beyond the seating position, to the position shown in dot-dash lines in which it is easier for the user to get on or off the seat. A vibration damping shock absorber 20 is mounted between a rocker lever 18 connected to the roller 15 and the base-plate 7, and rubber buffers 22 limit downward movement of the seat under load.

FR2309367 (A2) discloses a tractor seat supported by crossed levers, spring loaded and damped, fitted between the floor mounting (7) and the rigid plate (2) to which the seat is fitted. To alter the characteristics of the suspension, a spring loaded pivoted lever (51) is mounted under the seat support plate, with the spring (18) pulling the lever into a vertical setting. The bottom end of the lever rests against a roller (52) fitted at the end of an adjustable bar (59) the horizontal displacement of which is controlled by a threaded spindle (19) and a control knob (62). The control moves a pointer (63) over a calibrated scale to allow the driver to adjust the seat springing to suit his weight.
DISADVANTAGES WITH THE PRIOR ART

The main disadvantage with the systems currently being used for controlling the vibrations generated in the tractor seats is that the existing isolators can help in achieving a reduction of vibrations in Z direction only.

However, a metal sleeve needs to be inserted in these isolators to achieve a better isolation and the sleeves sit on the mounting surface and bolts are connected to this mounting surface.

Moreover, the size of such vibration isolators needs to be increased for obtaining a satisfactory isolation. But this raises the cost thereof significant and also poses serious assembly issues.

However, the above prior art documents teach to reduce the vibrations only in the Z direction. The suspensions in both the mentioned methods will help in providing a stiffness and damping to reduce the force or vibration transfer from source to receiver, in Z direction only. Since these systems do not provide stiffness and damping in other two directions, i.e. in X and Y directions, the vibrations or excitations will reach the receiver through the suspension system, without getting attenuated. Further, the suspension systems provided in the above prior arts are mainly focused on reducing the road excitations which is in the range of 0-20Hz. In addition, the use of springs, dampers and sophisticated mechanism will lead to higher product cost, thus these suspension systems cannot be used in products in the lower end of price band. The frequencies above 20Hz are usually attenuated with the help of isolation technique.

The isolators normally used can attenuate vibrations in Z direction only and not in X and Y directions.

Therefore, there is an existing need for controlling the vibrations generated in the tractor seats in all direction, i.e. in X, Y, Z directions.

OBJECTS OF THE INVENTION

Some of the objects of the present invention - satisfied by at least one embodiment of the present invention - are as follows:

An object of the present invention is to provide a tractor seat with a configuration having six degrees of freedom (6DoF).

Another object of the present invention is to provide a tractor seat which can control vibrations in all six possible modes of vibrations.

Still another object of the present invention is to provide a tractor seat which can control vibrations induced by road excitations as well as engine operation.

Yet another object of the present invention is to provide a cost-effective tractor seat.

A further object of the present invention is to provide a tractor seat which is easy to manufacture and assemble.

A still further object of the present invention is to provide a tractor seat having 6DoF, which requires minimal modification for implementation of the same in the existing designs.

A yet further object of the present invention is to provide a tractor seat having 6DoF, which targets at vibration levels in the range of 20-80Hz.

An even further object of the present invention is to provide a tractor seat having 6DoF, whereby vibrations in X, Y and Z directions are attenuated effectively.

These and other objects and advantages of the present invention will become more apparent from the following description, when read with the accompanying figures of drawing, which are however not intended to limit the scope of the present invention in any way.
SUMMARY OF THE INVENTION

Six degree of freedom (6DOF) tractor seat is designed in a such way that a complete control is achieved over all 6 modes of vibrations, i.e. forward and backward (surge), up and down (heave), left and right (sway) translation in three perpendicular axes, combined with the changes in orientations through rotation about three perpendicular axes termed as pitch, yaw, and roll. Unlike the conventional rubber isolators used in seats, the rubber isolators of the 6DOF tractor seat configured in accordance with the present invention, enable 100% isolation from the mounting surface, thereby facilitate in achieving zero vibration transmission from the mounting surface. This tractor seat with 6DOF also eases manufacturing and assembly processes of the tractor seats.

In accordance with the present invention, there is provided a tractor seat assembly for attenuating road excitations and to reduce the vibrations induced by tractor engine in all six degrees of freedom, the seat assembly comprising:

• a seat;
• a seat mount;
• a seat base; and
• a plurality of suspension elements;

wherein the seat assembly is mounted on the tractor skid and the suspension elements are placed between the seat mount and seat base to make an integrated connection for providing six degrees of freedom to the seat assembly.

In an embodiment of the present invention, the suspension elements are disposed at four corners of the seat mount connected to the seat base by means of a plurality of bolts.

In another embodiment of the present invention, the suspension elements are configured as spring damping units for transferring or attenuating the forces or excitations in all six directions based on the stiffness and damping characteristics thereof in each of the possible six degrees of freedom.
In still another embodiment of the present invention, the suspension elements are configured as isolators circular in shape with a definite height and having no metal-to-metal contact to provide 100% isolation between the vibration source and the seat.

In yet another embodiment of the present invention, each isolator comprises:

• an outer metal bracket rigidly mounted on the seat base;
• an inner metal bracket inserted inside this outer metal bracket,
• a guide for metal sleeve; and
• a bolt or pin inserted into the guide;

wherein the inner metal bracket acts as the support for a guide for connecting the seat to the seat base without any metal-to-metal contact therebetween.

In a further embodiment of the present invention, the guide is made of rubber.

In all embodiments of the present invention, the tractor seat assembly for attenuating road excitations and to reduce the vibrations induced by tractor engine in all six degrees of freedom, the seat assembly comprising: a seat; a seat mount; a seat base; and four isolators each disposed at one of the four corners of the seat mount connected to the seat base by means of a plurality of bolts.

In a further embodiment of the present invention, the isolators act as spring damping units for transferring or attenuating the forces or excitations in all six directions based on the stiffness and damping characteristics thereof in all six degrees of freedom.

In a still further embodiment of the present invention, the isolators are configured circular in shape with a definite height and having no metal-to-metal contact to provide 100% isolation between the vibration source and the seat.

In a yet further embodiment of the present invention, each isolator comprises:

• an outer metal bracket rigidly mounted on the seat base;
• an inner metal bracket inserted inside this outer metal bracket,
• a rubber guide for metal sleeve; and
• a bolt or pin inserted into the rubber guide;

where in the inner metal bracket acts as the support for the rubber guide to connect the seat to the seat base without any metal-to-metal contact there between.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

The present invention will be briefly described with reference to the accompanying drawings, in which:

Figure 1a shows a schematic representation of all six degrees of freedom possible in any three-dimensional space.

Figure 1b shows a schematic representation of the conventional scissor seat.

Figure 1c shows a perspective view of a modern scissor type tractor seat.

Figure 1d shows a side view of the seat back suspension of a conventional tractor seat.

Figure 1e shows a perspective view from the bottom of a conventional tractor seat.

Figure 2 shows a simple schematic diagram of 6DOF seat configured in accordance with the present invention.

Figure 3a shows an exploded view of the seat assembly configured in accordance with the present invention having six (6) degrees of freedom.
Figure 3b shows the construction of the isolators for seat of Figure 1.

Figure 4 shows a graphical representation of the vibration versus amplitude for comparing the conventional seat with the seat configured having 6DOF in accordance with the present invention.

DETAILED DESCRIPTION OF THE ACCOMPANYING DRAWINGS

In the following, the tractor seat having six degrees of freedom (6DoF) configured in accordance with the present invention will be described in more details with reference to the accompanying drawings without limiting the scope and ambit of the present invention in any way.

Figure 1a shows a schematic representation of all six degrees of freedom possible in any three-dimensional space. These are forward F and backward B (i.e. surge), up U and down D (i.e. heave), left L and right R (i.e. sway) motions during translation in three perpendicular axes, combined with the changes in orientations through rotation about three perpendicular axes termed as pitch P, yaw Y, and roll Rl.

Figure 1b shows a schematic representation of the conventional scissor seat. The scissor seat has a scissor mechanism. It is a combination of two slider crank mechanisms. The slider on top carries the spring, while the bottom one carries the damper.

Figure 1c shows a perspective view of a modern but conventional scissor type tractor seat of Figure 1b. It includes flex bellows at the bottom, which masks the mechanism.

Figure 1d shows a side view of the seat back suspension of a conventional tractor seat. This is also a simple slider crank mechanism carrying the suspension system. Here, crank means the bottom rod connecting to the seat base. The seat base itself forms the connecting rod. The slider is disposed inside a housing, which connects to the seat back.
Figure 1e shows a perspective view from the bottom of a conventional tractor seat depicting the suspension system at the seat back.

Figure 2 shows a simple schematic diagram of 6DOF seat configured in accordance with the present invention. All 6 DOFs are identified as 3 translational degrees of freedom (x, y, z) and 3 rotational degrees of freedom (?x, ?y, ?z) along the 3 coordinate axes. Each spring (S1, S2, S3, S4) in this diagram represents a spring damper unit and the stiffness and damping thereof are the actual stiffness (Kx, Ky, Kz) and damping (Cx, Cy, Cz) of the isolators used. Further, an important point characteristic here is that because of the isolators being circular in shape and having a definite height, the stiffness (Kx, Ky, Kz) can be generated along all three directions. Therefore, the stiffness (Kx, Ky, Kz) and damping (Cx, Cy, Cz) along these three directions helps in achieving all 6DOFs for the tractor seat. It helps in identifying all 6 Degrees of Freedom in the seat assembly. It also helps in developing a mathematical model for this 6 DOF seat.

Figure 3a shows an exploded view of the seat assembly configured in accordance with the present invention having six (6) degrees of freedom. Here, the seat 02 is mounted on a seat mount 04 disposed over a seat base 06. For example, four (4) isolators 08 are placed between the seat mount 04 and seat base 06. This can be made as an integrated connection and thus the seat mount 04 becomes an integral part of the seat 02. The seat mount 04 is connected to the seat base 06 with the help of a plurality of bolts. Since the bolts as well as an isolator mounting plate being connected on the tractor skid, does not have any metal to metal contact, it provides 100% isolation between the vibration source and the seat 02. To understand the isolation mechanism, it is necessary to have a look at the construction of isolators.

Figure 3b enlarged perspective view of the isolators 08 of Figure 3a.

Figure 3c shows the construction of the isolators 08 of Figure 3a. Here, an outer metal bracket 14 is rigidly mounted on the seat base 06. An inner metal bracket 12 is inserted inside this outer metal bracket 14. This inner metal bracket 12 acts as the support for an inner rubber tube 10. A bolt or pin can be inserted into a guide 16 for metal sleeve, so that seat 04 can be connected to the seat base 06 without making any metal to metal contact between these two 04, 06.

Figure 4 shows a graphical representation of the vibration versus amplitude (in the frequency range of 20 to 80Hz) for comparing the conventional seat with the seat configured having 6DOF in accordance with the present invention. Accordingly, the speed (rpm) and tachometer reading Tacho1 (T1) is shown on the ‘x’ axis, whereas the amplitude (RMS) and acceleration (m/s2) are shown on the ‘y’ axis. The curve drawn in Red color shows the characteristics of the conventional tractor seat, while the curve drawn in green color represents the characteristics for the six degrees of freedom (6DoF) seat configured in accordance with the present invention. This diagram shows a distinct significant improvement in the vibration levels. The 6DOF seat shows considerable improvement in vibration levels.

WORKING OF THE INVENTION

Figure 2 shows the schematic diagram of current invention. SK and SB are the seat mounting and seat base respectively. SB sits on SK and the connection is made through four suspension elements S1, S2, S3 & S4. Each suspension element S1, S2, S3 and S4 has stiffness (Kx, Ky, Kz) and damping (Cx, Cy, Cz) in all three directions. The linear displacements and angular displacements (x and ? respectively) are also shown along all three axes. The forces or excitations in any direction are transferred though the suspension elements due to the stiffness and damping in each direction. This helps in reducing the vibration transfer or attenuates the excitations in each direction.

TECHNICAL ADVANTAGES AND ECONOMIC SIGNIFICANCE

The tractor seat having six degrees of freedom (6DoF) as proposed in accordance with the present invention has the following technical and economic advantages:
• Applicable across all platform of applicant’s tractors.
• Easy to manufacture with minimal cost input.
• Requires minimal modification in the design stage w.r.t. the existing design.
• Includes very low cost service parts.

Throughout this specification the word “comprise”, or variations such as “comprises” or “comprising”, shall be understood to implies including a described element, integer or method step, or group of elements, integers or method steps, however, does not imply excluding any other element, integer or step, or group of elements, integers or method steps.

The use of the expression “a”, “at least” or “at least one” shall imply using one or more elements or ingredients or quantities, as used in the embodiment of the disclosure in order to achieve one or more of the intended objects or results of the present invention.

The exemplary embodiments described in this specification are intended merely to provide an understanding of various manners in which this embodiment may be used and to further enable the skilled person in the relevant art to practice this invention. The description provided herein is purely by way of example and illustration.

Although the embodiments presented in this disclosure have been described in terms of its preferred embodiments, the skilled person in the art would readily recognize that these embodiments can be applied with modifications possible within the spirit and scope of the present invention as described in this specification by making innumerable changes, variations, modifications, alterations and/or integrations in terms of materials and method used to configure, manufacture and assemble various constituents, components, subassemblies and assemblies, in terms of their size, shapes, orientations and interrelationships without departing from the scope and spirit of the present invention.

While considerable emphasis has been placed on the specific features of the preferred embodiment described here, it will be appreciated that many additional features can be added and that many changes can be made in the preferred embodiments without departing from the principles of the invention. These and other changes in the preferred embodiment of the invention will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the invention and not as a limitation.